Note: Descriptions are shown in the official language in which they were submitted.
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Carbon material
The invention relates to a carbon material, to a process
for preparing it and to its use.
EP 0 569 503 discloses a process for surface-modifying
carbon material with aromatic groups by electrochemical
reduction of a diazonium salt.
It is further known to provide carbon material with organic
groups by linking the organic groups to the carbon material
via a diazotization/azo coupling (WO 96/18688).
It is further known to provide carbon materials with
organic groups by bonding the organic groups to the carbon
material by means of reactions with free-radical formers
(Ohkita K., Tsubokawa N. and Saitoh E., Carbon 16 (1978)
41; DE 100 12 784.3) or via cycloadditions (DE 100 12
783.5). It is known to react carbon material with aliphatic
compounds possessing diazonium groups (JP 11315220 A;
Tsubokawa N., Kawatsura K. and Shirai Y., Int. Conf. Mater.
Proc. 12 (1997) 537; Tsabukoawa N., Yanadori K. and Sone
Y., Nippon Gomu Kyokaishi 63 (1990) 268). The compounds
used are aliphatic compounds and not aromatic diazonium
salt compounds. Bond formation between the compounds
containing diazonium groups and the carbon material takes
place through detachment of nitrogen and the formation of
free-radical species which can serve as starting functions
for further reactions (grafting).
It is likewise known to modify carbon material by reaction
with sulphuric acid or S03 (US 3,519,452; JP 2001-254033).
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JP 20011329205 discloses reacting carbon material in a two-
stage reaction first with OH-functionalized
cyclopentadienyl compounds and then with sulphuric acid.
Existing processes have the following disadvantages:
~ The diazotizing agents used, as well as the toxic and
oxidizing sodium nitrite, similarly include nonionic
organic nitrites, which are toxic and highly flammable.
Residues of the nitrites (counter-ions, alkyl radicals)
remain in the carbon material as an unattached impurity.
~ Nitrite has to be used in an acidic medium to carry out
the diazotization. Toxic oxides of nitrogen can form.
~ Free-radical formers are thermally or photochemically
labile, explosive and can lead to chain reactions which
are difficult to control.
~ Synthesis and purification of the free-radical formers'
precursor in some instances involve toxic or odour-
nuisance materials and hence are cost intensive with
regard to the manufacturing process, transport, use and
final disposal.
~ Cyclization reactions with nitrogenous heterocycles
proceed with nitrogen extrusion, which can lead to
sudden, explosive volume expansions or pressure rises
which significantly hinder smooth reaction management.
~ The reaction of carbon material with compounds that
possess azo groups and form free radicals by nitrogen
extrusion can likewise lead to sudden, explosive volume
expansions or pressure rises or else to thermal
difficult-to-control chain reactions and thus hinder
smooth reaction management.
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1 The reaction of carbon material with sulphuric acid or
oleum requires particularly durable, corrosion-resistant
and thermally stable materials; unwanted and hazardous
oxidations can occur as a secondary reaction; and the
neutralization needed after the reaction can generate
wastewaters having a high salt content, in which case a
portion of the generated salts can remain behind on the
carbon material as an impurity, and this can lead to
performance disadvantages.
1 The two-stage reaction with cyclopentadienyls and
sulphuric acid likewise has the disadvantage that
corrosion-resistant and thermally stable materials are
needed. Moreover, by-products, some of them soluble,
which can likewise lead to disadvantages, may arise in a
both quantitatively and qualitatively sizable amount.
Coloured by-products are disadvantages of existing carbon
materials having organic groups.
It is an object of the invention to provide a carbon
material having organic groups which contains little by way
of coloured by-products.
The invention provides a carbon material having organic
groups, characterized in that it is obtainable by the
reaction of carbon material with organic compounds of the
general formula l,
(1)
where X is O, S, NR' or PR', and
R1 - R' are the same or different and consist of H,
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acceptor groups, donor groups, alkyl or aryl groups having
acceptor and donor groups respectively, hydrophilic and/or
hydrophobic groups, or R1 - R' form cyclic systems which
are in turn substituted by acceptor or donor groups and/or
hydrophilic or hydrophobic groups.
The reaction of the carbon material with the organic
compound of the general formula 1 does not proceed via a
diazonium salt.
Acceptor groups may be -COORB, -CO-R8, -CN, -S02R$ or
-S020R8, where R8 is metal, H, alkyl, aryl, ammonium or
functionalized alkyl or aryl, for example c~~-carboxyalkyl,
HS03-CyHZ-, H2N-CyHZ- or H2N-S02-CyHZ- ( y = 1-4 5, z = 1-4 5 ) .
Donor groups may be SR9, ORg or N (R9) 2, where R9 is H,
alkyl, aryl or functionalized alkyl or aryl.
Hydrophilic groups may be S03M (M = metal), COOM or
-(CH2-CH2-0),.,-R9, where n = 1-45. Hydrophobic groups may be
alkyl, aryl, fluoroalkyl, perfluoroalkyl, fluoroaryl or
perfluoroaryl.
The organic groups R1 - R9 may be:
substituted or unsubstituted, branched or unbranched,
an aliphatic group, for example radicals from alkanes,
alkenes, alcohols, ethers, aldehydes, ketones, carboxylic
acids, esters, hydrocarbons, sulphonic acids, amines,
trialkylammonium salts, trialkylphosphonium salts or
dialkylsulphonium salts,
a cyclic compound, for example alicyclic hydrocarbons, such
as for example cycloalkyls or cycloalkenyls, heterocyclic
compounds, such as for example pyrrolidinyl, pyrrolinyl,
piperidinyl or morpholinyl groups, aryl groups, such as for
example phenyl, naphthyl or anthracenyl groups, or
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heteroaryl groups, such as for example imidazolyl, pyrazolyl,
pyridinyl, thienyl, thiazolyl, furyl or indolyl groups,
5 a heterocyclic compound containing nitrogen or further
heteroatoms and forming a three-, four-, five-, six- or more
highly membered ring which in turn is substituted by H, alkyl
or aryl groups having acceptor or donor substituents or parts
of cyclic systems having acceptor or donor substituents and/or
hydrophilic or hydrophobic groups,
substituted by further functional groups,
a chromophoric group or a dye or
suitable reactive compounds, such as for example
triarylammonium, triarylphosphonium, diarylsulphonium and
aryliodinium salts.
The group of the organic compounds of the general formula 1
may be tailored to the potential fields of use, since the
reaction principle permits for example not only the
introduction of hydrophilic but also the introduction of
lipophilic groups. The groups may also be ionic, polymeric or
further reactive. The groups may be used to modify different,
technically interesting properties of the carbon material in a
specific manner. For instance, the hydrophilicity of the
carbon material can be raised to such an extent that the
carbon material forms stable dispersions in aqueous media
without use of a wetting agent.
Compounds of the general formula 1 may be for example
compounds of the general formula 2 or 3
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~s XR~ Rya Rs
R~z Rz Rtz
\ \ ~ \ \
/ / R3 R~ ~ / / Rz
Rio Ra R,o Ra
2 3
where Rl-R6 are each as defined above and Rl°-R13 are the same
or different and consist of H, acceptor groups, donor
groups, alkyl or aryl groups having acceptor or donor
groups, hydrophilic and/or hydrophobic groups or R1° - R13
form cyclic systems which in turn are substituted by
acceptor or donor groups and/or hydrophilic or hydrophobic
groups.
The compounds of the general formula 1 may be for example:
OH OH OH
NHz
\ \
\ \
/ / /
/ / , S03Na , Na03S S03Na
NaO~S
OH
S03Na NHz ,
OH OH
\ \ ~ \ \ NHz ~ \ \
/ / ~ / / ~ / /
Na03S S03Na Na0 S
s
S03Na
OH NHz Na03S NH
\ \ 2
\
/ /
/ /
Na03S S03Na
OH
NHz
NHz S03Na
\ \ Na03S NH
/ ~ ~ \ \ ~ ( \ \ z
/ / / / '
S03Na
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NHz
S03Na
HzN \ \ OH \
\ \
/ / /
/ / ~ Na03S OH
COONa
NHz NHz NHz NHz
\ \ COONa \ OH \
/ / ,
/ , ~OH
COONa
COONa COONa
O NHz
NzH ~ ~ - O \ \
NH CHz~ ~ / / ,
ONa Na00C
/ OONa
\ \
N zl-I
,
OH
OH OH
\ \ ( \ \ ~ \ \ COONa
/ / , / / or / /
Na00C COONa
The abovementioned compounds can be used in the depicted
salt form or with some other counter-ion, for example K or
N (R9) 4.
Useful carbon material includes carbon black, graphite
powder, graphite fibres, carbon fibres, carbon fibrils,
carbon nanotubes, carbon fabrics, glassy carbon products,
activated carbon or fullerenes.
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Useful carbon black includes furnace black, gas black,
channel black, lamp black, thermal black, acetylene black,
plasma black, inversion black, known from DE 195 21 565,
Si-containing blacks, known from WO 98/45361 or DE 196 13
796, or metal-containing carbon blacks, known from
WO 98/42778, arc carbon and Boots which are by-products of
chemical manufacturing operations.
The invention's carbon material having organic groups
and/or the carbon material can be activated by means of
upstream reactions. These can be oxidation reactions for
example. Useful oxidizing agents include for example
ammonium peroxodisulphate, hydrogen peroxide, ozone, oxygen
(pure or as air), potassium bromide and/or sodium
perborate.
Carbon materials used as a reinforcing filler in rubber
mixtures can be used. Pigment grade carbon blacks can be
used. Useful carbon materials further include: conductivity
black, carbon material for UV stabilization, carbon
material useful as a filler and in systems other than
rubber, such as for example in bitumen or plastics, or
carbon material useful as a reducing agent in metallurgy.
The present invention further provides a process for
preparing the invention's carbon material having organic
groups, the process being characterized in that carbon
material is reacted with organic compounds of the general
formula 1.
The reaction of the carbon material with the organic
compound of the general formula 1 does not proceed via a
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diazonium salt; that is, no diazonium salt is used or
formed during the reaction.
The organic compound of the general formula 1 can be
applied to the carbon material by spray-drying a dispersion
comprising the carbon material and compound of the general
formula l, mixing or spraying. The organic compound of the
general formula 1 may be applied as a powder, as a melt or
as a solution. It may be particularly advantageous to apply
the organic compound of the general formula 1 during the
preparation of the carbon material, in which case the
organic compound of the general formula 1 is preferably
added at a position in the reactor that has the necessary
temperature. The reaction for modifying the carbon material
may preferably be carried out in the absence of a solvent
or else in a solvent, preferably a volatile organic
solvent. The reaction for modifying the carbon material may
be carried out at temperatures from -80°C to +300°C,
preferably from 80°C to 250°C. When the modifying takes
place during the production of the carbon material, the
temperatures may be between 250°C and 1500°C. The energy
input may be effected by means of mechanical energy,
vibrational energy, for example ultrasound, or
irradiational energy, for example microwave radiation, heat
radiation, light radiation, X-rays and electron beam
radiation. The reaction for modifying the carbon material
may be carried out in the absence of an oxidizing agent or
in the presence of an oxidizing agent (for example air,
hydrogen peroxide, peroxides, perborates, persulphates or
ozone).
The reaction of carbon material with compounds of the
general formula 1 can be carried out in a ratio of carbon
material to compound of the general formula 1 in the range
from 99.99:0.01 to 0.01:99.9. The ratio of carbon material
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to compound of the general formula 1 may preferably be in
the range from 50:1 to 1:50.
The reaction of carbon material with compounds of the
5 general formula 1 can be carried out in the pressure range
from 1 mbar to 250 bar. The reaction may preferably take
place in the pressure range 100 mbar to 50 bar.
The invention's carbon materials having organic groups can
10 be used as a filler, including as a reinforcing filler, a
UV stabilizer, as a conductivity carbon black or as a
pigment.
The invention's carbon materials having organic groups can
be used in rubber, plastics, inks, including solventborne
inks, waterborne inks, inkjet inks, xerographic toners,
coatings and paints, bitumen, concrete or other building
materials or paper. The invention's carbon materials can
further be used as a reducing agent in metallurgy. The
invention's carbon materials having organic groups can be
used for producing rubber mixtures, in particular for
producing tyres.
The invention further provides a dispersion characterized
in that it comprises the invention's carbon material having
organic groups and at least one solvent.
The organic group may be tailored to the particular
dispersion medium. Carbon materials modified with polar
organic groups may be particularly useful for polar media.
Polar media may be solvents, for example alcohols, ketones,
esters, acids, amines, glycols, glycol ethers or
halogenated solvents, but also oligomers or polymers having
polar groups, for example carbonyl, ester, amino, carboxyl
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and/or hydroxyl groups. Carbon materials having organic
groups, for example -S03W, COOW or OH, where W is H, alkali
metal ions or ammonium ions, can be particularly useful for
aqueous media. Hydrophobic modified carbon materials having
hydrophobic groups, such as alkyl, alkyloxy, aryl and/or
hetaryl, can be particularly useful for hydrophobic media
such as aliphatic, aromatic, heteroaliphatic and/or
heteroaromatic hydrocarbons. Media which in terms of their
polarity are between the relatively apolar, hydrophobic
media and the strongly polar media, for example ethers
and/or mixtures of polar and apolar media, may be
particularly suitably served by specifically adapted
modifications, for example with amino, carbonyl or halogen
substituents.
The dispersion of the present invention may further
comprise one or more additives, such as biocides, wetting
agents, ketones, glycols, alcohols or mixtures thereof.
These additives may be added for specific applications and
may also consist of monomeric, oligomeric or polymeric
compounds for example. These additives may effect
improvements in properties, such as degree of dispersion,
storage stability, freeze stability, drying behaviour,
foaming ability, wettability and/or bonding to certain
substrate materials, such as paper, metal, glass, polymers,
fibres, leather, wood, concrete or rubber.
The present invention further provides a process for
producing the dispersion of the invention, the process
being characterized in that the invention's carbon material
having organic groups is dispersed in at least one solvent
using a bead mill, an ultrasonicator, a high pressure
homogenizes, a microfluidizer, a rotor-stator assembly, for
example Ultra-Turrax, or a comparable assembly.
The dispersions of the present invention can be used in
rubber, plastics, inks, including solventborne inks,
waterborne inks, inkjet inks, xerographic toners, coatings
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and paints, bitumen, concrete and other building materials
or paper.
The dispersions of the present invention can be used for
coloration and for UV stabilization of plastics, latices,
textiles, leather, adhesives, silicones, concrete, building
materials, paper, fibres and earth or for antistatic
rendering of materials.
The invention's carbon materials having organic groups have
the advantage that
polar modified carbon materials (having S03M substituents
for example) are better dispersible in polar systems,
primarily water,
apolar modified carbon materials (having alkyl groups for
l5 example) are better dispersible in apolar systems, for
example oils,
suitably modified carbon materials having polar or
sterically bulky groups are stabilized electrostatically
and sterically, respectively, in the systems and require no
further auxiliaries, say wetting agents, for stabilization,
carbon materials modified by the process of the present
invention are better stabilized in dispersions and so have
better colour properties, such as depth of shade and
bluishness,
carbon materials modified by the process of the present
invention are by virtue of the broader variability of the
hydrophilic substituents better tailorable to specific
performance requirements (for example high optical density
and low intercolour bleeding in inkjet),
carbon materials having bound dyes have modified hues,
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carbon materials having still reactive substituents can be
utilized for coupling and crosslinking in systems (rubber
for example),
reactive modified carbon materials allow bonding of the
carbon materials to a polymer, and
carbon materials are producible that are low in by-
products, salts, acids and moisture.
Examples
The examples utilize Ruf3 S 160 black carbon. Rul3 S 160 is a
commercial product of Degussa AG.
Determination of pH:
pH is determined using a Schott CG 837 pH meter on the neat
suspension.
The glass electrode is dipped into the solution and the
temperature-corrected pH is read off five minutes later.
Determination of viscosity:
The rheology of the neat suspension is determined using a
Physica UDS 200 rheometer in a rotation test at controlled
rate of shear (CRS). The sample is temperature controlled
to 23°C. The viscosity value is read off at a shear rate of
1000 s-1.
Determination of surface tension:
Dynamic and static surface tension of a temperature
controlled sample at 20°C is determined using a Kruss BP2
bubble tensiometer. The final value is read off at 15 ms
for dynamic surface tension and at 3000 ms for static
surface tension.
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Example 1: Modification of carbon material with sodium 7-
amino-4-hydroxy-2-naphthalenesulphonate.
Na03S \ \ NH2
/ /
OH
4 g of 7-amino-4-hydroxy-2-naphthalenesulphonic acid are
suspended in 150 ml of water and made to dissolve by
stirring with 0.67 g of sodium hydroxide in 50 ml of water,
20 g of Ru(3 S 160 carbon black are added, then the solvent
is distilled off under reduced pressure and the remaining
mixture is heated to 180°C for 4 hours.
Example 2: Modification of carbon material in solid phase
with sodium 5-amino-2-naphthalenesulphonate.
NH2
\ \
/ /
Na03S
4 g of sodium 5-amino-2-naphthalenesulphonate and 20 g of
Ruf3 S 160 carbon black are mixed, 5 ml of water are added
dropwise, everything is mixed once more and the mixture is
then heated to 180°C for 4 hours.
Example 3: Modification of carbon material with sodium 5-
amino-2-naphthalenesulphonate.
4 g of sodium 5-amino-2-naphthalenesulphonate are suspended
in 150 ml of water and made to dissolve by stirring with
0.72 g of sodium hydroxide in 50 ml of water, 20 g of Ruff S
160 are added, then the solvent is distilled off under
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reduced pressure and the remaining mixture is heated to
180°C for 4 hours.
Example 4: Modification of carbon material with sodium
5 hydroquinonesulphonate.
OH
S03Na
OH
4 g of sodium hydroquinonesulphonate and 4.5 g of ammonium
peroxodisulphate are each dissolved in 150 ml of water and
added in succession to 20 g of Rule S 160 carbon black, then
10 the solvent is distilled off under reduced pressure and the
remaining mixture is heated to 180°C for 4 hours. The
modified carbon black is washed with 300 ml of water and
then dried at room temperature.
15 Example 5: Modification of carbon material with disodium
4,5-dihydroxy-2,7-naphthalenedisulphonate.
Na03S \ \ S03Na
/
OH OH
4 g of disodium 4,5-dihydroxy-2,7-naphthalenesulphonate are
dissolved in 200 ml of water and added to 20 g of Ruf3 S 160
carbon black. Then, 10 ml of 30 percent hydrogen peroxide
are added and the solvent is distilled off under reduced
pressure. The remaining mixture is heated to 180°C for
4 hours. The modified carbon black is washed with 300 ml of
water and then dried at room temperature.
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Example 6: Modification of carbon material in solid phase
with sodium 4-amino-3-hydroxynaphthalenesulphonate.
4 g of sodium 4-amino-3-hydroxynaphthalenesulphonate and
20 g of Rul3 S 160 carbon black are mixed, 3 ml of
30 percent hydrogen peroxide are added dropwise, everything
is mixed once more and the mixture is subsequently heated
to 180°C for 4 hours. The modified carbon black is washed
with 300 ml of water and then dried at room temperature.
Example 7: Modification of carbon material with disodium 4-
amino-5-hydroxy-2,7-naphthalenedisulphonate.
Na03S \ \ S03Na
/ /
OH NHZ
4 g of disodium 4-amino-5-hydroxy-2,7-naphthalene-
disulphonate were dissolved in 250 ml of water and added to
g of Rul3 S 1&0 carbon black and then the solvent is
distilled off under reduced pressure. The residue and 2.7 g
of ammonium peroxodisulphate are mixed and subsequently
20 heated to 180°C for 4 hours. The modified carbon black is
washed with 300 ml of water and then dried at room
temperature.
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Example 8: Modification of carbon material with sodium
6-amino-2-naphtholcarboxylate
COONa
N2H
4 g of 6-amino-2-naphtholcarboxylic acid are suspended in
200 ml of water, neutralized to pH 7.5 and dissolved by
stirring with 1 mol/1 NaOH solution. 40 g of Ru~3 S 160
carbon black are added, then the solvent is distilled off
under reduced pressure and the remaining mixture is heated
at 200°C for 4 hours.
Example 9: Dispersion of modified carbon material in water.
I5 g of carbon material having organic groups according to
Example 1 are stirred with 85 ml of water and subsequently
dispersed using an Ultra-Turrax at 5000 rpm for 30 minutes.
The dispersion obtained is stable without further addition
of wetting agent.
Dynamic surface tension at 15 ms: 78 mN/m
Static surface tension at 3000 ms: 69 Nm/m
pH: 6.5
Viscosity: 3.2 mPas
Example 10: Dispersion of modified carbon material in
water.
15 g of carbon material having organic groups according to
Example 2 are stirred with 85 ml of water and subsequently
dispersed using an Ultra-Turrax at 5000 rpm for 30 minutes.
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The dispersion obtained is stable without further addition
of wetting agent.
Dynamic surface tension at 15 ms: 82 mN/m
Static surface tension at 3000 ms: 71 Nm/m
pH: 7.2
Viscosity: 2.9 mPas
Example Il: Dispersion of modified carbon material in
water.
15 g of carbon material having organic groups according to
Example 3 are stirred with 85 ml of water and subsequently
dispersed using an Ultra-Turrax at 5000 rpm for 30 minutes.
The dispersion obtained is stable without further addition
of wetting agent.
Dynamic surface tension at 15 ms: 77 mN/m
Static surface tension at 3000 ms: 70 Nm/m
pH: 7.0
Viscosity: 2.7 mPas
Example 12: Dispersion of modified carbon material in
water.
15 g of carbon material having organic groups according to
Example 4 are stirred with 85 ml of water and subsequently
dispersed using an Ultra-Turrax at 5000 rpm for 30 minutes.
The dispersion obtained is stable without further addition
of wetting agent.
Dynamic surface tension at 15 ms: 81 mN/m
Static surface tension at 3000 ms: 70 Nm/m
pH: 7.5
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viscosity: 2.9 mPas
Example 13: Dispersion of modified carbon material in
water.
15 g of carbon material having organic groups according to
Example 8 are stirred with 85 ml of water and subsequently
dispersed using an Ultra-Turrax at 5000 rpm for 30 minutes.
The dispersion obtained is stable without further addition
of wetting agent.
Dynamic surface tension at 15 ms: 86 mN/m
Static surface tension at 3000 ms: 71 Nm/m
pH: 8.5
Viscosity: 2.7 mPas
